Inverse design in the complex plane: Manipulating quasinormal modes

Abstract

Utilizing the fact that the frequency response of a material can be decomposed into the quasinormal modes supported by the system, we present two methods to directly manipulate the complex frequencies of quasinormal modes in the complex plane. We first consider an "eigenpermittivity"approach that allows one to find how to shift the permittivity of the structure everywhere in order to place a single quasinormal mode at a desired complex frequency. Secondly, we then use perturbation theory for quasinormal modes to iteratively change the structure until a given selection of quasinormal modes occurs at desired complex frequencies.